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Isuzu Crank Identification Knowledge Pays Off In Real World Situation

Method of identifying the 3.5L crankshaft found on the front and rear counterweights

By Roy Berndt
Back in January of 2007 I did an article about the differences of the 1992-2004 3.2L Isuzu components and in particular the different crankshafts. I also remarked that the 3.5L crankshaft is identical in appearance and dimensions and that only the stroke is what made it different.

One part of that article worth discussing again is the method of identifying the 3.5L crankshaft found on the front and rear counterweights. There is a shallow groove machined into both of them on the OD (see Figure 1). However, this gets a little tricky sometimes because many cranks may have a "tooling drag" line on the OD of one of the counterweights. Don't be confused by a "tool drag" mark that I, too, have seen on many cranks: you must make certain that the distinctive groove is present on both the first and last counterweight.

Now, before you start thinking that I am a slacker who has packed it in for the year, started preparing for the holidays and that I'm just handing you a bunch of rehashed goods, let me tell you why I bring this up. The old school of hard knocks recently reared its ugly head at ProFormance Powertrain during a run of the 3.5L Isuzu engines.

During the final stages of assembly, while rotating one engine, it suddenly locked up. On the bottom end of the engine there is an oil manifold that bolts onto the top of the main bearing caps - the crankshaft assembly was hitting that manifold. Fortunately having a number of these engines sitting side by side in the same state of assembly we could easily see that none of the others were in the same condition. So why was there a problem with this particular engine? The oil manifold was different - it did not have reliefs in it like all the others (see Figure 2).

We soon discovered that the oil manifold without the relief notches as shown in Figure 2 was a manifold for the 3.2L Isuzu's shorter 77mm stroke crankshaft and that the manifold for the longer 85mm stroke crank in the 3.5L engine requires a little extra clearance. Now, you can certainly use the 3.5L manifold on a 3.2L but not vice versa. So if you ever have 3.2L and 3.5L engines in your facility at the same time you'll want to make certain that the right oil manifolds get on the right engines or you could have a serious problem if it somehow gets out of your building unnoticed.

Practical Builder Tip
Next I want provide a quick PBT (Practical Builder Tip) that has come a up a few times on an engine that we all know backward, forward and upside-down: the 350 Chevrolet. Not long ago, I came across a situation that made even me do a double-take. The 1996-2000 vintage 350 four bolt main block (c/n 10243880) can come with a water pump bypass hole or without (see Figures 3 and 4).

When the engine went to Vortec cylinder heads the water pump bypass was no longer needed, so the cylinder head (yes the head) no longer included a coolant port to accommodate the passage (see Figure 5).

What I forgot when confronted with this situation is that the water pump bypass port went from the front of the engine to an intersecting port/channel that ran vertically to the deck of the block, then met with a mating port on the cylinder head. Since the Vortec head does not have that port, even though your water pump may not cover the opening it's no big deal. There is no active coolant flow to the bypass hole anyway, so what difference does it make? None.

Of course, there are the doubting Thomases out there who will blow into that hole with shop air pressure (100+ PSI). In such a case you will get bubbles in the cooling system because the system was not designed to withstand that high of pressure. Try blowing with 22-25 psi and it will be sealed tighter than a drum. So when you get that "my water pump does not cover the lower hole on of the block on the driver's side" call, remember this: if it is a Vortec engine you have no worries – there is no coolant there anyway.